The monitoring of movements of monitored individuals involves a variety of sectors, including parolees and home confinement. The technology has its roots in the home arrest systems of the 1980's, in which a user wearable component—typically a “beacon” anklet that was locked to the monitored individual—would communicate wirelessly with a stationary base unit. The range was limited to a few feet of the radio frequency transmitter and receiver. The base unit included a telephone connection for communicating with the authorities. If the monitored individual left the short range allowed by the equipment, the tag and the base unit would lose contact and the base unit would respond by sending an alert to the authorities. False alarms for minor deviations from the short range and/or an inability to confirm false from actual alarms (if the person was where they were supposed to be when the police arrived to investigate) desensitized the police to such alerts, rendering the technology of limited application to low risk offenders.
A later generation of the technology incorporated GPS and cellular telephone technology in a locked anklet. The device would actively record the location of the monitored individual over time and transmit the data to a central monitoring location (e.g., police or parole monitoring services). The central location could store and analyze the data for prohibited movements (e.g., a sex offender near a school) or cross reference the movement data with crime data to see if the monitored individual was near the crime at the time of the crime. U.S. Pat. Nos. 5,867,103, 6,160,481, 6,218,945, 6,512,456 and 6,703,936, incorporated herein by reference in their entireties, are each exemplary of such a system. The technology is also used to monitor other individual sectors (e.g., patients, children) and objects (e.g., cars, cargo).
The modern monitoring device includes a GPS receiver that determines location, a memory that stores location data over time to define a movement history, and a cellular modem that communicates the movement history to a central location through the cell network. A common implementation is in the criminal justice system as an alternative to incarceration, and monitored individuals (typically parolees) have tamper resistant devices attached to their leg. For ease of discussion embodiments herein are directed to parolees, although the invention is not so limited.
Often monitored individuals are prohibited from interacting with each other. For example, in some jurisdictions parolees are not allowed to congregate, even socially, outside of approved environments (e.g., parole office, halfway house). Physical interactions between monitored individuals can be identified by overlap in the their movements as reported by their monitoring devices, as the movement data from the monitoring devices would show that monitored individuals were at the same place at the same time. Such interactions can be flagged for reporting to supervising authorities in near real time.
A limitation on the above tracking technology is that it cannot identify or track interactions between monitored individuals and unmonitored individuals. Thus for example, monitored individual A could meet with an unmonitored individual in the morning, and then the unmonitored individual could meet with monitored individual B later in the day. The unmonitored individual could thus act as a go-between to relay items, information or communication between monitored individuals A and B. This interaction will not be identified by the movement data, as the monitored individuals A and B were never in physical proximity with each other at the same time.